How to execute JavaScript on Android?

Question

I have code which uses ScriptEngineManager, ScriptEngine class for executing JavaScript code using Java. But it works fine in Java SE, and doesn\'t work in Android - SDK sh

Answer 1

You can use Webview which inherits View class. Make an XML tag and use findViewById() function to use in the activity. But to use the JavaScript, you can make a HTML file containing the JavaScript code. The example blelow might help.

Webview browser=(Webview) findViewById(R.main.browser); //if you gave the id as browser
browser.getSettings().setJavaScriptEnabled(true); //Yes you have to do it
browser.loadUrl("file:///android_asset/JsPage.html"); //If you put the HTML file in asset folder of android

Remember that the JS will run on WebView, not in native environment, thus you might experience a lag or slow FPS in emulator. However when using on an actual phone, the code may run fast, depending on how fast is your phone.

Answer 2

AndroidJSCore is a great one. And here is another little library I wrote for evaluating JavaScript:

https://github.com/evgenyneu/js-evaluator-for-android

jsEvaluator.evaluate("function hello(){ return 'Hello world!'; } hello();", new JsCallback() {
  @Override
  public void onResult(final String result) {
    // get result here (optional)
  }
});

It creates a WebView behind the scenes. Works on Android version 3 and newer.

Answer 3

Given that ScriptEngineManager and ScriptEngine are part of the JDK and Android SDK is not the same thing as the JDK I would say that you can't use these classes to work with JavaScript under Android.

You can check the Android SDK's reference documentation/package index to see what classes are included (what can you work on Android out of the box) and which of them are missing.

Answer 4

I was also looking for a way to run javascript on Android and came across j2v8 library. This is a java wrapper for Google's v8 engine.

To use it add a dependency:

compile 'com.eclipsesource.j2v8:j2v8_android:3.0.5@aar'

It has pretty simple api, but I haven't found any docs online apart from javadoc in maven repository. The articles on their blog are also useful.

Code sample from this article:

public static void main(String[] args) {
    V8 runtime = V8.createV8Runtime();

    int result = runtime.executeIntegerScript(""
        + "var hello = 'hello, ';\n"
        + "var world = 'world!';\n"
        + "hello.concat(world).length;\n");

    System.out.println(result);

    runtime.release();
}